If this is your first visit, be sure to
check out the FAQ by clicking the
link above. You may have to register
before you can post: click the register link above to proceed. To start viewing messages,
select the forum that you want to visit from the selection below.

• During recent maintenance and software update, account email addresses were reset. Consequently email notifications of private messages and posts to subscribed threads, as well as password recovery could not be sent.

• Please go to your Settings (click on "Settings" in the upper right corner of any page), then go to "Edit Email & Password" in the left menu bar under "My Account". Make sure your current and valid email address is listed and click on "Save Changes" whether you changed anything or not.

• This will update your email notification settings and you should start receiving them again.

• Be sure to use a VALID email address!! If you make any changes, you will receive an email to verify the changes made to your account. You will need to click on the link in the email in order to carry on.

A work colleague, fully aware of my skills with building ridiculous flash lights, asked me if I could do something with his 2xAA mini-mag. Having never even held one let alone modified one I jumped at the chance. I want to go all out and have settled on a triple XP-G mod like here. I'm going to copy that build pretty much exactly, starting with powering the emitters in parallel using this driver. My question however is how much current the driver is pulling from the cells.

Considering I plan to use 2 series connected protected 14500 cells the current draw can't be very high. Am I right in reading the table provided on the drivers sale page that states that with 7.2V input, the driver will only draw 0.17A, 0.85A and 1.6A from the cells to provide it's 0.25A, 1.38A and 2.8A output current? 7.2V in is a lot when you consider I only need about 3.15V across each emitter. Being that that are in parallel we're looking at 1W, 5.5W and 11.3W of heat for each drive level! That's a lot of heat in such a small package...

Is my maths correct? Does the driver function as I expect?

I can't really think of any other driver to use as the 14500 cells are pretty limiting. Any suggestions!?

The circuit works as a buck driver (reduces the voltage) so the input of 7.2V at 1.6A , is stepped down to give 3A output at around 3V (the LED Vf).
So you are right there.

This means you connect the LED's in parallel, the voltage will still be 3V, but the current is divided by 3, i.e. each LED should get about 1A each.

As for the power and heat, Power in is 7.2V * 1.6A = 11.3W
Power out on high, assuming 90% efficiency is ~10.3W

This means 1W is lost at heat in the driver (you need to heatsink the large black chip on the topside of the driver)
And then 10.3W is going to the LED's, so it will get hot!

I have used the same driver in a Mag 2C mod driving a SSC P7, it got warm but handled the heat fairly well.
I know there are a few other drivers out there that will give the same output etc, but i've never used them... they also look a tad taller.

Ah OK so the driver's current draw from the batteries is correct and within spec of the cells? That was my main concern. I did explain to the guy I'm building it for that he can't expect to run it on high for very long at all. Better start working on that heat sink....

Ah OK so the driver's current draw from the batteries is correct and within spec of the cells? That was my main concern. I did explain to the guy I'm building it for that he can't expect to run it on high for very long at all. Better start working on that heat sink....

AW 14500's are labelled 900mAH, and usually measure pretty close to that. Being LiCo cells, the max safe discharge rate is 2C, meaning 1.8A.

If you're going to be pulling 1.6A, make sure you have good cells - that sort of current draw will be too high for cheap cells.

If LiCo 14500's are going to be a limiting factor for safe operation, what about AW IMR 14500's? They are rated for 4 amps continuous discharge.

mvyrmnd has made the same observation. The guy I'm basing my build on used trustfire flame cells and seemed to have no problems. I'll see how they handle and if I feel they get too hot I'll recommend a set of IMR AW cells.

mvyrmnd posted about LiCo's, I'm suggesting IMR's - both AW but very different chemistry: IMR's are far better for high discharge applications.
I guess you're feeling lucky about going with Trustfires then.

mvyrmnd posted about LiCo's, I'm suggesting IMR's - both AW but very different chemistry: IMR's are far better for high discharge applications.
I guess you're feeling lucky about going with Trustfires then.

Sorry I got myself confused with the battery chemistry's. I'm still learning.

As for the Trustfires...I live on the edge lol. I think i'll get the guys light working first and then strongly recommend IMR 14500's. The Trustfires are cheap enough, just have to be careful.

I think that driver is bigger than you realize. Are you sure it will fit in the 2AA light?

Hmmm well the site says 17mm - and that will fit in the head of the light which is where I intend on using it. If not I'm sure I can find another application for it :-)

Wow, I completely missed that. I think this is the first inexpensive 3A buck driver I've heard of this size. Please let us know your impressions of it and if a standard 16.8mm driver pill can accept one with little trimming.

Oh, wait, check out the user comment with the subject "size"... on 4/16/2012 someone reported: I just got one and it's 19(mm)....not what I was expecting..